/* ============================================
   US Stock Insight Pro - 主样式文件
   独特类名前缀：usp- (US Stock Pro)
   零外部依赖 | 移动端优先 | PageSpeed 优化
   ============================================ */

/* === 1. CSS Reset & Base === */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    font-size: 16px;
    -webkit-text-size-adjust: 100%;
    scroll-behavior: smooth;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
    line-height: 1.6;
    color: #111827;
    background-color: #F9FAFB;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

img {
    max-width: 100%;
    height: auto;
    display: block;
}

a {
    color: #1E40AF;
    text-decoration: none;
    transition: color 0.2s ease;
}

a:hover {
    color: #1E3A8A;
    text-decoration: underline;
}

/* === 2. 布局系统（独特前缀 usp-）=== */
.usp-wrapper {
    width: 100%;
    max-width: 1280px;
    margin: 0 auto;
    padding: 0 1rem;
}

@media (min-width: 768px) {
    .usp-wrapper {
        padding: 0 2rem;
    }
}

/* Grid 系统 */
.usp-layout-grid {
    display: grid;
    gap: 2rem;
}

.usp-grid-cols-1 {
    grid-template-columns: repeat(1, 1fr);
}

@media (min-width: 768px) {
    .usp-grid-cols-md-2 {
        grid-template-columns: repeat(2, 1fr);
    }
    
    .usp-grid-cols-md-3 {
        grid-template-columns: repeat(3, 1fr);
    }
    
    .usp-col-span-2 {
        grid-column: span 2;
    }
}

/* Flexbox 工具类 */
.usp-flex {
    display: flex;
}

.usp-flex-wrap {
    flex-wrap: wrap;
}

.usp-items-center {
    align-items: center;
}

.usp-justify-between {
    justify-content: space-between;
}

.usp-gap-1 { gap: 0.25rem; }
.usp-gap-2 { gap: 0.5rem; }
.usp-gap-4 { gap: 1rem; }
.usp-gap-6 { gap: 1.5rem; }
.usp-gap-8 { gap: 2rem; }

/* === 3. 颜色系统 === */
:root {
    --usp-color-primary: #1E3A8A;
    --usp-color-primary-dark: #1E40AF;
    --usp-color-secondary: #2563EB;
    --usp-color-accent: #FBBF24;
    --usp-color-accent-dark: #F59E0B;
    --usp-color-text: #111827;
    --usp-color-text-light: #4B5563;
    --usp-color-text-muted: #9CA3AF;
    --usp-color-bg: #F9FAFB;
    --usp-color-bg-white: #FFFFFF;
    --usp-color-border: #E5E7EB;
}

.usp-bg-primary { background-color: var(--usp-color-primary); }
.usp-bg-accent { background-color: var(--usp-color-accent); }
.usp-bg-white { background-color: var(--usp-color-bg-white); }
.usp-bg-gray-50 { background-color: #F9FAFB; }
.usp-bg-gray-100 { background-color: #F3F4F6; }
.usp-bg-gray-800 { background-color: #1F2937; }
.usp-bg-blue-50 { background-color: #EFF6FF; }

.usp-text-white { color: #ffffff; }
.usp-text-primary { color: var(--usp-color-primary); }
.usp-text-accent { color: var(--usp-color-accent); }
.usp-text-gray-900 { color: #111827; }
.usp-text-gray-800 { color: #1F2937; }
.usp-text-gray-600 { color: #4B5563; }
.usp-text-gray-500 { color: #6B7280; }
.usp-text-gray-400 { color: #9CA3AF; }

/* === 4. 排版系统 === */
.usp-text-xs { font-size: 0.75rem; line-height: 1rem; }
.usp-text-sm { font-size: 0.875rem; line-height: 1.25rem; }
.usp-text-base { font-size: 1rem; line-height: 1.5rem; }
.usp-text-lg { font-size: 1.125rem; line-height: 1.75rem; }
.usp-text-xl { font-size: 1.25rem; line-height: 1.75rem; }
.usp-text-2xl { font-size: 1.5rem; line-height: 2rem; }
.usp-text-4xl { font-size: 2.25rem; line-height: 2.5rem; }

@media (min-width: 768px) {
    .usp-text-4xl { font-size: 3rem; line-height: 1.2; }
}

.usp-font-bold { font-weight: 700; }
.usp-font-extrabold { font-weight: 800; }
.usp-font-medium { font-weight: 500; }
.usp-font-semibold { font-weight: 600; }

.usp-uppercase { text-transform: uppercase; }
.usp-tracking-tight { letter-spacing: -0.025em; }
.usp-tracking-widest { letter-spacing: 0.1em; }

.usp-leading-relaxed { line-height: 1.625; }

.usp-line-clamp-2 {
    display: -webkit-box;
    -webkit-line-clamp: 2;
    -webkit-box-orient: vertical;
    overflow: hidden;
}

/* === 5. 间距系统 === */
.usp-p-2 { padding: 0.5rem; }
.usp-p-4 { padding: 1rem; }
.usp-p-6 { padding: 1.5rem; }
.usp-p-8 { padding: 2rem; }

.usp-py-2 { padding-top: 0.5rem; padding-bottom: 0.5rem; }
.usp-py-3 { padding-top: 0.75rem; padding-bottom: 0.75rem; }
.usp-py-4 { padding-top: 1rem; padding-bottom: 1rem; }
.usp-py-8 { padding-top: 2rem; padding-bottom: 2rem; }

.usp-px-4 { padding-left: 1rem; padding-right: 1rem; }
.usp-px-8 { padding-left: 2rem; padding-right: 2rem; }

.usp-mt-2 { margin-top: 0.5rem; }
.usp-mt-4 { margin-top: 1rem; }
.usp-mt-6 { margin-top: 1.5rem; }
.usp-mt-8 { margin-top: 2rem; }

.usp-mb-2 { margin-bottom: 0.5rem; }
.usp-mb-4 { margin-bottom: 1rem; }
.usp-mb-8 { margin-bottom: 2rem; }

.usp-mx-2 { margin-left: 0.5rem; margin-right: 0.5rem; }
.usp-mx-auto { margin-left: auto; margin-right: auto; }

.usp-space-y-2 > * + * { margin-top: 0.5rem; }
.usp-space-y-4 > * + * { margin-top: 1rem; }
.usp-space-y-6 > * + * { margin-top: 1.5rem; }

/* === 6. 边框 & 阴影 === */
.usp-border { border: 1px solid var(--usp-color-border); }
.usp-border-t { border-top: 1px solid var(--usp-color-border); }
.usp-border-b { border-bottom: 1px solid var(--usp-color-border); }
.usp-border-t-4 { border-top: 4px solid var(--usp-color-secondary); }

.usp-rounded { border-radius: 0.25rem; }
.usp-rounded-md { border-radius: 0.375rem; }
.usp-rounded-lg { border-radius: 0.5rem; }

.usp-shadow-sm { box-shadow: 0 1px 2px 0 rgba(0, 0, 0, 0.05); }
.usp-shadow-md { box-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1); }

/* === 7. 按钮组件 === */
.usp-btn {
    display: inline-block;
    padding: 0.75rem 2rem;
    font-weight: 700;
    font-size: 1.125rem;
    border-radius: 0.375rem;
    transition: all 0.2s ease;
    cursor: pointer;
    border: none;
    text-align: center;
    line-height: 1.5;
}

.usp-btn-primary {
    background-color: var(--usp-color-primary);
    color: #ffffff;
}

.usp-btn-primary:hover {
    background-color: var(--usp-color-primary-dark);
    text-decoration: none;
}

.usp-btn-accent {
    background-color: var(--usp-color-accent);
    color: var(--usp-color-text);
}

.usp-btn-accent:hover {
    background-color: var(--usp-color-accent-dark);
    text-decoration: none;
}

.usp-btn-full {
    width: 100%;
}

/* === 8. 头部导航 === */
.usp-site-header {
    background-color: var(--usp-color-primary);
    color: #ffffff;
    padding: 1rem 0;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
    position: sticky;
    top: 0;
    z-index: 1000;
}

.usp-brand-title {
    font-size: 1.5rem;
    font-weight: 700;
    letter-spacing: -0.025em;
    color: #ffffff;
}

.usp-brand-title a {
    color: #fff;
}

.usp-brand-title a:hover {
    text-decoration: none;
}

.usp-highlight {
    color: var(--usp-color-accent);
}

.usp-main-nav {
    display: none;
}

@media (min-width: 768px) {
    .usp-main-nav {
        display: flex;
        gap: 1.5rem;
        font-size: 0.875rem;
        font-weight: 500;
    }
    
    .usp-main-nav a {
        color: #ffffff;
        transition: color 0.2s ease;
    }
    
    .usp-main-nav a:hover {
        color: var(--usp-color-accent);
        text-decoration: none;
    }
}

/* === 9. Hero Section === */
.usp-hero {
    background-color: #ffffff;
    padding: 2rem;
    border-radius: 0.5rem;
    box-shadow: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    border-top: 4px solid var(--usp-color-secondary);
    margin-bottom: 2rem;
}

.usp-hero-badge {
    color: var(--usp-color-secondary);
    font-weight: 700;
    font-size: 0.75rem;
    text-transform: uppercase;
    letter-spacing: 0.1em;
}

.usp-hero-title {
    font-size: 2.25rem;
    font-weight: 800;
    margin-top: 0.5rem;
    margin-bottom: 1rem;
    color: #1F2937;
}

@media (min-width: 768px) {
    .usp-hero-title {
        font-size: 3rem;
    }
}

.usp-hero-description {
    font-size: 1.25rem;
    color: #4B5563;
    line-height: 1.625;
    max-width: 48rem;
}

/* === 10. 文章卡片 === */
.usp-article-card {
    display: flex;
    gap: 1rem;
    background-color: #ffffff;
    padding: 1rem;
    border-radius: 0.25rem;
    box-shadow: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    border: 1px solid var(--usp-color-border);
    transition: border-color 0.2s ease;
}

.usp-article-card:hover {
    border-color: #BFDBFE;
}

.usp-article-title {
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--usp-color-primary);
}

.usp-article-title:hover {
    text-decoration: underline;
}

.usp-article-meta {
    margin-top: 0.75rem;
    display: flex;
    align-items: center;
    font-size: 0.75rem;
    color: var(--usp-color-text-muted);
}

.usp-meta-item {
    display: inline-flex;
    align-items: center;
    gap: 0.25rem;
}

.usp-meta-sep {
    margin: 0 0.5rem;
}

.usp-icon {
    width: 16px;
    height: 16px;
}

/* === 11. 侧边栏组件 === */
.usp-sidebar-widget {
    background-color: #EFF6FF;
    padding: 1.5rem;
    border-radius: 0.5rem;
}

.usp-widget {
    background-color: #ffffff;
    padding: 1.5rem;
    border-radius: 0.5rem;
    border: 1px solid var(--usp-color-border);
}

.usp-widget-title {
    font-weight: 700;
    font-size: 1.125rem;
    margin-bottom: 1rem;
    color: var(--usp-color-primary);
}

.usp-trending-item {
    background-color: #ffffff;
    padding: 0.5rem;
    border-radius: 0.25rem;
    border: 1px solid #DBEAFE;
    font-size: 0.875rem;
}

.usp-trending-keyword {
    font-weight: 600;
    color: var(--usp-color-primary-dark);
    text-decoration: underline;
}

/* === 12. Newsletter 表单 === */
.usp-newsletter-box {
    background-color: #1F2937;
    color: #ffffff;
    padding: 1.5rem;
    border-radius: 0.5rem;
}

.usp-widget-newsletter {
    background-color: #1F2937;
    color: #ffffff;
}

.usp-newsletter-title {
    font-size: 1.25rem;
    font-weight: 700;
    margin-bottom: 0.5rem;
    color: #fff;
}

.usp-newsletter-desc {
    color: var(--usp-color-text-muted);
    font-size: 0.875rem;
    margin-bottom: 1rem;
}

.usp-newsletter-input {
    width: 100%;
    padding: 0.5rem;
    border-radius: 0.25rem;
    background-color: #374151;
    border: none;
    color: #ffffff;
    margin-bottom: 0.5rem;
}

.usp-newsletter-input::placeholder {
    color: #9CA3AF;
}

/* === 13. 底部 Footer === */
.usp-site-footer {
    background-color: var(--usp-color-bg);
    border-top: 1px solid var(--usp-color-border);
    margin-top: 3rem;
    padding: 2.5rem 0;
}

.usp-footer-section h5 {
    font-weight: 700;
    color: #1F2937;
    margin-bottom: 0.5rem;
}

.usp-footer-section p {
    line-height: 1.625;
}

.usp-footer-links {
    margin-top: 2rem;
    padding-top: 2rem;
    border-top: 1px solid var(--usp-color-border);
    display: flex;
    flex-wrap: wrap;
    gap: 1rem;
    font-size: 0.75rem;
}

.usp-footer-links a {
    color: var(--usp-color-secondary);
    text-decoration: underline;
}

.usp-footer-copyright {
    text-align: center;
    margin-top: 2rem;
    font-size: 0.75rem;
    color: var(--usp-color-text-muted);
}

/* === 14. 面包屑导航 === */
.usp-breadcrumbs {
    padding: 1rem 0;
    font-size: 0.875rem;
    color: var(--usp-color-text-light);
}

.usp-breadcrumb-sep {
    margin: 0 0.5rem;
    color: var(--usp-color-text-muted);
}

/* === 15. 文章详情页 === */
.usp-article-header {
    margin-bottom: 2rem;
}

.usp-article-title {
    font-size: 2rem;
    font-weight: 700;
    color: var(--usp-color-text);
    margin-bottom: 1rem;
}

.usp-article-intro {
    background-color: #EFF6FF;
    border-left: 4px solid var(--usp-color-secondary);
    padding: 1rem 1.5rem;
    margin-bottom: 2rem;
    font-size: 1.125rem;
    line-height: 1.75;
}

.usp-article-body {
    font-size: 1.125rem;
    line-height: 1.75;
    color: #374151;
}

.usp-article-body h2 {
    font-size: 1.75rem;
    font-weight: 600;
    margin-top: 2rem;
    margin-bottom: 1rem;
    color: var(--usp-color-text);
}

.usp-article-body h3 {
    font-size: 1.5rem;
    font-weight: 600;
    margin-top: 1.5rem;
    margin-bottom: 0.75rem;
    color: var(--usp-color-text);
}

.usp-article-body p {
    margin-bottom: 1rem;
}

.usp-article-body ul,
.usp-article-body ol {
    margin-left: 1.5rem;
    margin-bottom: 1rem;
}

.usp-article-tags {
    margin-top: 2rem;
    padding-top: 2rem;
    border-top: 1px solid var(--usp-color-border);
}

.usp-tag-link {
    display: inline-block;
    background-color: #EFF6FF;
    color: var(--usp-color-primary);
    padding: 0.25rem 0.75rem;
    border-radius: 0.25rem;
    margin-right: 0.5rem;
    margin-bottom: 0.5rem;
    font-size: 0.875rem;
}

.usp-tag-link:hover {
    background-color: var(--usp-color-secondary);
    color: #fff;
    text-decoration: none;
}

.usp-article-nav {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 1rem;
    margin-top: 2rem;
    padding: 1.5rem 0;
    border-top: 1px solid var(--usp-color-border);
}

.usp-nav-prev,
.usp-nav-next {
    padding: 1rem;
    background-color: #F9FAFB;
    border-radius: 0.5rem;
    font-size: 0.875rem;
    transition: background-color 0.2s ease;
}

.usp-nav-prev:hover,
.usp-nav-next:hover {
    background-color: #EFF6FF;
    text-decoration: none;
}

.usp-related-list {
    list-style: none;
    padding: 0;
}

.usp-related-item {
    padding: 0.5rem 0;
    border-bottom: 1px solid var(--usp-color-border);
}

.usp-related-item:last-child {
    border-bottom: none;
}

/* === 教育声明框 === */
.usp-education-notice {
    padding: 0.75rem 1rem;
    background-color: #EFF6FF;
    border-left: 4px solid #2563EB;
    font-size: 0.875rem;
    color: #374151;
    margin-top: 1rem;
    border-radius: 0.25rem;
}

.usp-link-underline {
    text-decoration: underline;
    font-weight: 600;
}

.usp-text-gray-300 {
    color: #D1D5DB;
}

.usp-text-gray-300:hover {
    color: #FFFFFF;
}

/* === 16. WhatsApp 按钮 === */
.usp-whatsapp-btn {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    background-color: #25D366;
    color: #ffffff;
    padding: 0.75rem 1.5rem;
    border-radius: 2rem;
    font-weight: 600;
    transition: background-color 0.2s ease;
}

.usp-whatsapp-btn:hover {
    background-color: #128C7E;
    text-decoration: none;
}

.usp-whatsapp-icon {
    width: 24px;
    height: 24px;
}

/* === 17. 工具类 === */
.usp-hidden { display: none; }
.usp-inline-block { display: inline-block; }
.usp-w-full { width: 100%; }
.usp-max-w-3xl { max-width: 48rem; }
.usp-text-center { text-align: center; }
.usp-underline { text-decoration: underline; }

.usp-transition {
    transition: all 0.2s ease;
}

/* === 18. Print 样式 === */
@media print {
    .usp-site-header,
    .usp-site-footer,
    .usp-newsletter-box,
    .usp-whatsapp-btn,
    .usp-sidebar {
        display: none;
    }
}